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So for example I chose 38 psi long ago (108,000 miles) because
1. sotp feel WAY hard past 38 psi
2. diminishing returns @ 40 psi.
(hope I am not being vaque here)
(I stopped at 44 due to the fact this is the max tire sidewall pressure for most tires)
and either decide to get the MAX (least) and "suffer" through a harder ride or like what I did, chose 38 psi, which happens to be halfway point between the psi with the best reduction in rolling resistance on the graph.
In any case, thanks for posting the graph, for if rolling resistance is a priority, it confirms what took a certain amount of trial and error to get a handle on.
So a next logical variable would be: the effect of say 24 psi vs 40 psi on fuel mileage. So what does 40 psi (21% reduction in rolling resistance) convert to mpg wise (all things being equal of course). vs 24 psi.
In a daily commute we get 48-52 mpg. So if I pick a half way of 45 (epa ratings) and real world 50.5, would I be correct in saying the 5.5 mpg/50.5 or 11% mpg GAIN is due to running 38 psi when 26 psi was recommended?
IF that is true, then percentage ratios are thus: a 19.5% reduction in rolling resistance (38 psi)= -3.5%=
-16.5% decrease in rolling resistance= 11% gain in mpg
Stretching it further, could it also account for roughly 2x the tread life? Anecdotal information indicates this tire lasts to 40,000 to 50,000 miles (for most owners of like sized tires and of course brand) This set looks good to go to the next rotation @ 110,000 miles to go to a min of 120,000 miles.
It would seem that the right amount of (HOT) air really goes a LONG WAY? (app 2 to 2.4 X's).
Oh well...live and learn. Next time will spend a bit more and get a Yokahama or Sumitomo tire instead. Still love the Civic though and can imagine how much better it would drive with some better sneakers...like the Turanza LS-T's that I had on my last car.
The Sandman
I have been running two Toyo products (diverse) 1. TPT's 2. Proxes 3. Ultra (there is a newer one) the nexus being good rain performance, and important to me, close to oem rolling resistance aka littel to no mpg loss.
To tell you truthfully it doesn't rain much around here, so....
On the Toyo Proxes I ran it once in the rain going from Las Vegas NV to Monument Valley and compared to running the oem GY Eagle F1 Super Cars in the rain, which has fierce dry grip, it was like running on rails in the rain.
I am looking at the Bridgestone Potenza RE960AS Pole Position in the stock 205/55R16 size. If my budget fails me, the G019 and BFGoodrich Traction T/A are also on my list of possibilities. I think the Subaru actually handles pretty well and I think a performance oriented tire will be a nice complement to the suspension's capabilities.
I think the Accord will need to get shocks (it feels pretty under-damped to me) and a plus-1 fitment to get any kind of performance out of that car. A softsport spring kit wouldn't hurt either, maybe it wouldn't feel as high as an SUV then.
The Sandman
Krzys
Is Yokahama considered low end... middle.. or high? I hear different things.
I put on 4 new Yokahama Avid T4 tires about 2 years ago. For the price at the time $58 per tire (15" tire) installed, lifetime rotation... they've been very good tires. Seem to be wearing a bit more than they should for a 70k mile tire. :sick:
BFG actually seems to be doing pretty well across the board from the Traction TA on up. My Comp TA R1s were fantastic at the time.
Khumo's low end highway tire is not so great, but their entry level performance tires have been well received.
Worry more between comparable models and less about brand name.
So to attribute a difference in actual fuel economy from the standardized fuel economy test results to a difference in tire pressure ...... well ..... ah ....... how do I say this nicely? Mmmmm, it's a bit oversimplifying the situation.
The same is true for treadwear. Straight ahead driving results in better wear than turning corners. Increasing pressure improves the situation, but be careful of over simplifying the cause and effect.
To put this in perspective, the results of the standardized EPA fuel economy test has been broken down into components - and tires account for about 17% of the fuel consumption in this test. So changing tires should have some fraction of the 17% change.
However, if your driving conditions are different than the EPA test, then not only will your fuel economy be different, but the affect any particular change to the vehicle is going to have is also going to be different.
For example, if you were to take out all the interior - seats, door upholstery, headliner, etc. - the weight reduction would result in an improvement in FE. But, this weight reduction would only affect the acceleration portion of the test and not the steady state portion of the test.
Tires, on the other hand, would mostly affect the steady state portion of the test.
So be careful assigning any difference to the difference in pressure.
Nor have I. My posts were indeed questions. The 38psi-36 psi and 38-34 psi, were probably one of the few consistent measures. So if I understand you correctly, if I put in 26 psi, instead of 38-36. 38-34 psi, I would have achieved the same results? Indeed, that would even contradict the graph you posted!?
Thanks for taking a shot anyway. Nothing you have said explains the reality.
If I were to characterize and factor in the conditions how I drive, according to your post, I would posit the tires to have lasted to app 40,000 miles and most likely LESS miles. I also would have gotten less than EPA mileage (consistently) That would be obviously not be the reality.
So for example, I do not believe GY slipped me their new experimental (magical) mind blowing tires, Stop and go driving is really the essence of our daily commute. Higher speed highway driving is the norm here. (80-95 mph)
So evidently, neither you nor I can explain why ( in my estimation) these low rated tires have lasted app 3x longer than "normal". Almost by definition my driving conditions are "different" that the standardized and "idealized" EPA conditions. So again how can I be nice, but just to say: ivory tower vs brutal reality (from a tire perspective).
However, I continue to remain surprised and happy that the tires have exceeded almost all expectations (per web site of like TDI Jetta owners) . I by no means (as you can probably surmise) consider myself babying (the car and) tires. Indeed when I took the vehicle for a (first) 105,000 mile alignment check, the owner of a well respected (local) VW performance shop (who also did the alignment) looked at me a bit cock eyed as I answered his questions, how many miles on the tires, when did you do the last alignment.
And exactly how old are those tires?
..."So be careful assigning any difference to the difference in pressure."...
......."
Opps! Gotta work on my typing skills. What I meant was be careful assigning 100% of any difference to the difference in pressure.
A couple of additional thoughts: You have a 2003 with aver 105,000 miles - That's more than 20,000 miles per year. This is quite a bit more than the norm.
From this I would speculate (without any additional information) that you are driving less "stop and go" than the EPA test cycle and that would result in better fuel economy and better tire wear - and that's what you've got.
So not everything is coming from the increased tire pressure. - and that's what I was trying to say.
We can also put it into context of the yearly average of betwen 12,000-15,000 miles per year. That would be 12-15/21.6= 44% to 31% more mileage.
However GIVEN those factors how would you address the opposite end, if 26 psi were use vs 38 psi (etc etc)?
If they have, what is the difference the Primacies offer? Are they "better"? If so, in what ways?
Eh, X-number of miles warranty is a crock, and so is the treadwear rating. The tire companies self-assess both of those ratings, there is no governance over them, so they are only comparable within the same brand.
I was thinking of model as like high performance all season, touring all season, or standard all season or something like that. Even within those categories, some brands are more of a bargain than others, and the cheapest tire isn't always the best value.
I think the worst tire I've ever had was the Cooper Sport 1000, it lasted every bit of its "warranty" and inexpensive, but it made the car scary to drive in rain, added many feet to its stopping distances, and was loud. Contrast that to the Khumo ASX in the same price range (but different category) which handled great (even in snow, let alone rain), had great stopping distances, and was all around fun tire.
I think price is part of the value equation, but lowest cost isn't always the best route (I used to be a big fan of Yokos with the A509, the AVS intermediate and the AVS Sport, but less so lately).
After following tire discussions, a few other (important to me) factors stand out, but the above is the essential equation.
So for example, oem GY LS-H's 5 ea @ 95 (475)+80 (R/R/B=555./120,000 (or whatever you project/target your mileage to be)=.004625 cents per mile driven (so far).
I think that is only true of cost is your only criteria; that is certainly not the case for me.
After following tire discussions, a few other (important to me) factors stand out, but the above is the essential equation.
I would say value is more important than total cost.
[ 4* $ 118 (205/55R16 Bridgestone RE960 A/S Pole Position)]/[3 yrs * 12000 mi/year]=$ .0131/ mile
Having a responsive handling vehicle that can swerve or brake to avoid hazardous situations = Priceless :P
Volkswagen Golf TDI - 1.9L turbodiesel (100 hp) 5A + ABS 60-0 141 (GY LS)
Volkswagen GTI 2.0t 127 ft (conti sportcontact)
Hmm, 14', thats almost a car length...and an insurance deductible is $500...how do we factor that?
Judgement:
PRICELESS.
Judgement:
PRICELESS.
Oh, I forgot, you are a highly skilled professional behind the wheel. I am sure you will understand that you are in a very elite group and most don't share your passion or pride in your driving skillset. For this reason, I like to be able to avoid collisions caused by the carelessness of others (and I am sure since you share my love of driving, would never be someone like yourself).
In addition to doing my best to be an alert driver, I also enjoy driving and part of that for me is the feel of a responsive car. Rock hard tires that do little to grip the road really don't inspire me. I am willing to pay extra for a performance tire that makes the car feel good to me. I am also willing to pay for an extra margin of safety provided by a more performance oriented tire. My Benjamins, my prerogative.
I am not saying your decision is bad, you have criteria you use to make your purchase decisions and that is great; it works well for you. It is just very different than mine.
Hardly, but that is the good thing! You don't have to be a highly skilled professional driver to have and/or develop good judgement!
It is absolutely true about they being your nickels.! All the best.
Sometimes you do not have a choice, you use what is presented to you and then having better handling tires can save not only your money but your life too.
Krzys
Just goes to show that you are saying it is possible to crash anything, even a Z06 Corvette, with monster grip tires (1500 per set) and 1 lateral G. capability.
You still make the case that judgement is still priceless.
In certain novice classes for autocross, you aren't allowed any modifications to the vehicle at all, and you have to use tires with a treadwear rating over a certain number. Pretty much the only modification you can make is tire pressure. White shoe polish is used where the sidewall meets the tread and across the face of the tire so the driver can see what the contact patch looked like during the run.
Slightly over-inflating the front tires seems to reduce understeer in corners, while the rear inflation pressure can be modified to increase "rotation." This comes with a slight penalty in ride quality, seems to increase tramlining, and can shorten tire life but making the wear uneven, but eh, for short periods of time under controlled settings, who cares, its kinda fun.
What brand of tires, what psi, and how long have they lasted? Just curious to see what you're getting on a performance vehicle vs. the rest.
I just wish the Accord had a more performance oriented tire size as opposed to the Buick level 205/60R16s. I am hoping by the time those tires wear out, either I no longer own the car or I can score some 17s and go for 215/50R17s that might have a more enthusiast friendly tire option. And as long as I am whining, the Accord could use some more damping and it wouldn't kill it to be ~1" lower.
I think it also has a lot to do with the tire's durometer/MOH which is tied into the treadwear rating (sort of).
So you are saying that tread is softer? Like it has a lower durometer?
UTQG ratings are based on a set of 3 test procedures - one for each parameter.
In the case of treawear it is about a 7,500 miles test over a prescribed course in Texas. The tire being tested is compared against the SRTT (Standard Reference Test Tire) This is a particular tire is used for testing where a control tire is needed, because test conditions will cause differences in results - traction testing being where the concept came from. Treadwear tests are always comparative tests.
The problem is that the SRTT is a particular size and will only fit on certain vehicles. If I remember correctly, the current SRTT is a moderate sized 15" passenger car tire. Needless to say, large SUV tires won't have a common vehicle so that the test can be conducted - SO ..... the regulations allow the test to be run comparing 2 tires with a known tire that is TRACEABLE back to the SRTT.
This where the myth comes from that you can not compare UTQG treadwear ratings between brands. While it is true, that a tire manufacturer will no doubt test against its own tires - the test results still trace back to the SRTT.
HOWEVER ...... Because treadwear testing is highly variable, it becomes a bit of a shell game, and while the treadwear rating has some meaning, it certainly has plenty of "wiggle" room.
To further complicate things, the regulations say that a tire manifacturer is allowed to understate the ratings. Put another way, a certain tire could pass a "AA" traction rating but because of marketing, they may decide to only post an "A" rating. The same holds true for the treadwear rating - it can not be overstated, but it can be understated.
It is common for certain tire lines to be tested in several sizes and then the worst case becomes the rating. With OE tires, this is particularly true. Vehicle manufacturers set the specifications, so there is very little consistency across all the sizes in that line. So they are frequently understated.
Since the above discussions have involved OE tires, you have to take into account that the UTQG rating is set up for a worst case scenario. In other words, the tire you are discussing may have been designed for good treadwear (and therefore deliver poor traction), but the UTQG treadwear rating may not reflect this, but the traction rating will. And vice versa.
This sort of problem doesn't exist for tire lines designed for the replacement market - and because this is a fairly competitive area, the UTQG ratings are generally closely stated and can be fairly reliably compared between tire brands.
So take the treadwear ratings with a grain of salt - and maybe the whole shaker - and be aware of how they are derived and when you can use them and when you can't.
BTW, NHTSA does check on these ratings and from time to time a tire manufacturer has to explain where he gets his numbers from.
Has anyone else heard of this new directive by Michelin? These Primacy tires have a 60k mile warranty, so I don't know whether to worry about excessive tire or not. Any thoughts? Thanks! :confuse:
What is counterintuitive: the tires with the LEAST tread (not legally bald @ 2/32 nd) actually have the BEST dry grip !! Intuitively compared to tires with the most tread, more worn tires have less wet grip. So at some point, the driver with at least 2 points reminding him the "least wet capable tires" are on the front, raining and can feel hydroplaning will actually slow down due to those factors which actually DOES decrease the chances of spinning out.
Loss of traction of the front tires under acceleration, braking, etc.. can usually be easily remedied by slowing down and/or turning the wheel...
Loss of traction by the rear tires, means a skid and loss of control.. Possibly recoverable, but requiring much more skill (and luck).
It is counter-intuitive, especially on a front wheel drive vehicle... But, ask any racer where you need the best rubber..
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Later I saw why.
But, the same tire chain will rotate the tires 6000 miles later and put the ones that were new and on the rear onto the front with the worn front ones now going to the rear. Duh.
There is little difference in the slight imbalance front to rear after 6000 miles...
2014 Malibu 2LT, 2015 Cruze 2LT,
I guess I just never thought of it like that. I used to get so frustrated on the track with understeer and the total lack of rotation that I would pray for the back end to come lose.
Loss of traction by the rear tires, means a skid and loss of control.. Possibly recoverable, but requiring much more skill (and luck).
Yeah, I think that is the way the stability control systems are designed too, to keep the back from passing the front, even if it means a collision vs a spin. I think weight transfer plays a big role in this too. In a FWD car though, keeping steady throttle and steering where the car needs to go will catch a lot of fishtails.
It is counter-intuitive, especially on a front wheel drive vehicle... But, ask any racer where you need the best rubber..
In the track event driving schools, for FWD vehicles we were basically taught to keep your foot in it and steer where you want the car to go. You typically have the overwhelming amount of weight up front and the suspensions are set up to understeer right off the road, so trail braking and doing anything you can to break the back end to let the car rotate is the order of the day. That is why FWD racers will stagger tires with the bigger tires in the front, so help rotation.
So for examples, (Bridgestone Potenza RE 960 pole position a/s)
G .93 dry -G .88 wet G=.05 G/.93= - 5.4%
Stopping Distance (50-0) wet 92.4 ft- dry 87.8=4.6 ft /92.4 ft= - 5 %
BTW, Michelin lost the lawsuit on this subject.